The present invention relates to an electromagnetic interference suppressing body for use in suppressing electromagnetic interference by any useless or undesired electromagnetic wave or waves, and also relates to an electric circuit device using the electromagnetic interference suppressing body.
In digital and/or high frequency electric circuit devices, small size and light weight are strongly desired and, therefore, electronic parts are required to be mounted on a printed circuit board as well as in an electric circuit device with a high density.
When electronic parts and wiring conductive lines are mounted on a circuit board, electromagnetic interference is caused by electrostatic and/or magnetic coupling between electronic parts and/or wiring conductive lines. Further, if a plurality of circuit boards are disposed adjacent to one another, electromagnetic interference is also caused between the adjacent circuit boards. In particular, the electromagnetic interference is severe when active elements such as semiconductor devices are mounted on the circuit board or boards because the active elements radiate undesired electromagnetic wave or inductive noise.
In the prior art, suppress of the electromagnetic interference was tried by means of connecting a low-pass filter or noise filter to each output terminal of the circuit board or by means of keeping a circuit in question at a distance. However, they require a space for disposing the filter or filters and/or a space for giving the distance. As a result, the device is made large in size and weight.
For suppressing electromagnetic coupling between adjacent circuit boards, a conductive shielding member was disposed between the circuit boards. However, the shielding member cannot prevent reflection of an undesired radiation from one circuit board, so that the reflection increases magnetic coupling between parts on the circuit board.
Hybrid integrated circuit elements are known as electronic circuit elements of a high density and a small size and are usually mounted on a mother board or boards in the electric circuit device. In the condition, the hybrid integrated circuit elements also suffer from electromagnetic interference.